What to do this month in the Iris Garden

In the Northern Hemisphere the Iris are dormant beginning in November and on through February, in many areas well into March even. 

Remove all spent bloom stalks and dead foliage. Trim Iris foliage to a height of about 6 inches. A clean garden will help prevent the spread of various fungal diseases and can discourage overwintering pests from building nests.

Evergreen boughs or straw make a good winter protection for Iris, particularly in areas with especially harsh winters. Apply after freeze-up. Heaving of the soil, caused by freeze-thaw patterns, can result in the dislodging of the rhizome. Avoid mulches that will trap moisture around the rhizome, as this environment can induce rot. Remove winter protection promptly in the early spring when new foliage begins sprouting.

If you live in area with mild winters, no winter protection is necessary. Keep the Iris garden free of weeds and grass throughout the winter. 

Spring is inevitable no matter how high the snow banks or how low the mercury. When all threat of frost has passed, remove the winter protection. If the garden is still covered in snow and ice, leave winter protection in place. If the ground is clear of snow and ice, you may see weeds and grass begin to emerge. Get them while they're young, and before their roots become long and difficult to remove.

 

Dwarf Iris often emerge in late March, depending on the weather. We recommend you bait for slugs, and continue all through the spring and summer. Use a type of bait that is wildlife and pet friendly! Pull or spray weeds. Get them while they’re small and the ground is soft! Control grass and trim away from Iris beds. (“Grass Be Gone”, available in most garden centers, is safe and effective around Iris. Follow manufacturer's instructions closely.) Remove any winter protection when new Iris growth begins to emerge. Watch for signs of Iris borers if they are a problem in your area. Visit our "How to Grow & Care for Bearded Iris" pages for more details on controlling pests in the Iris garden.

When getting ready for fertilizing, here is a good rule of thumb: Apply Iris fertilizer when the tulips are blooming in your neighborhood. Bone meal, superphosphate, or a general fertilizer with a 6-10-10 balance are all effective. Be sure to read manufacturer's recommendations for your soil type. Avoid using any fertilizer high in Nitrogen, such as fresh manure, because too much Nitrogen encourages rapid foliage production instead of blooms, and can lead to rot. If fertilizers are applied, avoid placing them directly on the Iris rhizomes as this can burn and injure them. Apply as a top dressing around the plant and work into the soil.

Spring means taking action against our least desirable garden inhabitants
– weeds and pests. Here we recommend a few tasks to help prepare for a successful Iris bloom season:

• Spray for fungus, such as leaf spot. Trim affected foliage and discard in the trash, not the yard debris. Use a garden fungicide. Always follow manufacturer's instructions.
• As soon as you see new Iris foliage sprouting, clear off dead leaves and other forms of winter protection.
• Ensure that garden soil drains well. 
• With bacterial and crown rots, remove and destroy any infected plant parts to avoid the spread of these diseases to healthy plants nearby 
• When Tulips bloom in your area, it is time to fertilize your Tall Bearded Iris. Avoid  the use of fresh manure. We recommend a fertilizer low in Nitrogen, such as a 6-10-10 mix. Too much Nitrogen can increase foliage growth, decrease bloom development, and lead to rhizome rot. We carry a 1 lb. bag of specially formulated Iris food.
• For areas with Iris Borers, read our page on this topic under the "Tips on Growing & Maintaining Bearded Iris" pages.

Bearded Iris bloom season is here at last, and all your year-round gardening efforts have paid off! Enjoy the glorious colors this month. Here are a few cultural tips recommended to keep your Iris beds in top form throughout the bloom season.

• Pull weeds out of Iris beds. Get them while they’re small!

• Bait for slugs using the pet and nature friendly method or product of your choice.

• Remove any diseased or brown leaves, but leave the healthy green foliage undisturbed. You can trim any leaves affected by "leaf spot" at the point just below the affected area (leaving as much of the healthy leaf intact).

• Dead-head spent blooms throughout bloom season. Remove the bloom stalk by cutting it at the base when all blooms are finished on that stalk.

• Stake taller stems to prevent them from tipping over in the wind and rain.

• About one month after all blooms are done, apply a light application of fertilizer and water in. Bone meal, superphosphate and 6-10-10 are all effective. Use fertilizer LOW in Nitrogen. Too much nitrogen can lead to rot problems.

• Keep Iris beds free of weeds.

Summertime is the season for planting Iris. Iris need to be planted at least 6 weeks before the first hard frost to ensure they are well established before winter. 

In this context "planting" refers to both new plants you have ordered (or received from a friend) and the act of dividing and transplanting older Iris clumps. We recommend dividing Iris clumps and replanting every 3-5 years.

You should divide and transplant Reblooming Iris every year or two for better chances of second bloom.

When planting, apply a low-Nitrogen fertilizer, bone meal or superphosphate to give the plants a healthy start in their new location.

When planting new Iris label your Iris with weather-proof plant markers. Perhaps create a map of your garden beds to help identify your Iris year to year.

Keep Iris beds free of weeds all summer long.

How much water do Iris need in the summer?  Water newly planted Iris once very well at planting time, then again every couple weeks. A gentle tug on the top of the foliage is a good test to see if the new roots have set in. Established Iris beds need very little water during the summer. However, a periodic deep watering can keep the Iris foliage looking fresh all summer long. Over-watering, though, can lead to rot. Avoid excess moisture. Ensure that the soil drains well. Reblooming Iris like more water in the summer to encourage rebloom.

Mark your newly planted Iris with weather-proof labels so that you know what's blooming where when spring arrives. Consider making a map of your garden.

Now is a good time to introduce or add Beardless Iris to your garden. Plant Siberian and Louisiana Iris.

Keep Iris beds free of weeds and grass.

 

To avoid over wintering insects and diseases that can cause rot, and to reduce the occurrence of leaf spots and borers, remove and destroy any garden debris, spent Iris bloom stalks, and brown dry foliage each fall.

 

Cut back remaining foliage to about 6” above the rhizome (this is not required, and is really up to the individual gardener). Trimming the foliage, however, does have its benefits:  the garden appears tidier, and the surface area on which leaf spot (a fungus) can develop is reduced.

In the Northern Hemisphere the Iris are dormant now. You might even see new increases. Clean off the old, mushy leaves to prevent the growth and spread of various fungal diseases. The dead leaves are also perfect hideouts for insects.

Evergreen boughs or straw make a good winter protection for Iris, particularly in areas with especially harsh winters. Apply after freeze-up. Heaving of the soil, caused by freeze-thaw patterns, can result in the dislodging of the rhizome. Avoid mulches that will trap moisture around the rhizome, as this environment can induce rot. Remove winter protection promptly in the early spring when new foliage begins sprouting.